Stream Sampling via Differential Pressure The unit connects to the 1.5" soft water feed line. An integrated transmitter creates a slight pressure drop, diverting a continuous sample stream to the internal sensor for constant monitoring. The Resin Shrinkage & Expansion Principle The unit's core is a calibrated shrink-resin sensor capsule (Part #: 370 031). It works as follows: Normal Soft Water: In soft water containing sodium ions, the indicator resin beads inside the capsule remain fully expanded. Hardness Breakthrough: When the softener is exhausted, hard water with calcium (Ca²⁺) and magnesium (Mg²⁺) ions enters. This causes the resin beads to shrink sharply and immediately. Magnetic Reed Contact Switching This change in resin volume alters the height of the resin column. A small magnet embedded in the sensor assembly moves along with the resin. As the resin shrinks, the magnet moves past a reed contact switch, closing the contact and triggering a signal. Signal Export for System Integration The Limitron is designed for machine integration. The contact signal is wired to a digital fault input on the facility's PLC or RO system microprocessor. When tripped, it sends a "Hard Water Fault" signal to the processor. This allows the system to initiate pre-programmed responses, such as activating a bypass or shutting down the RO pump to prevent scaling. Key Operational Requirements for the 1.5" Model For accurate readings, follow these three rules: Flow Rates: This model is designed for flow rates between 1.50 m³/h and 16.0 m³/h. Upstream Pressure Protection: Maintain feed water pressure between 2 and 6 bar. Install an overpressure protection valve upstream to prevent pressure spikes from compressing the resin. Sensor Capsule Handling: After a hardness breakthrough, replace or regenerate the capsule. Always store spare capsules in soft water or RO permeate to prevent them from drying out.